1. Field of the Invention
The present invention relates to liquid discharge heads for discharging liquids and methods for manufacturing the liquid discharge heads. The present invention particularly relates to a liquid discharge head for discharging ink onto a recording medium and also relates to a method for manufacturing the liquid discharge head.
2. Description of the Related Art
An example of a process using a liquid discharge head is an ink-jet recording process for discharging a liquid onto a recording media. An ink-jet recording head suitable for use in an ink-jet recording process includes fine discharge ports, a liquid channel, and energy-generating elements for generating energy used to discharge a liquid present in a portion of the liquid channel.
U.S. Pat. No. 5,478,606 discloses a method for manufacturing an ink-jet recording head suitable for use in an ink-jet recording process. In the method, a soluble resin pattern for an ink (liquid) channel is formed on a substrate having energy-generating elements. The following layer is deposited on the ink channel pattern: a resin coating layer, containing an epoxy resin and a cationic photopolymerization initiator, for forming walls of the ink channel. Discharge ports are formed in the resin coating layer by photolithography so as to be located above the energy-generating elements. The soluble resin is removed by dissolution, and the resin coating layer is then cured, whereby the ink channel walls are formed.
In such a process, the exposure operation used to form the ink channel pattern and the photolithography used to form the discharge ports require great attention to detail as described below. If light is applied to a first surface of the resin coating layer that is opposite to the substrate, the intensity of the light is reduced while the light is traveling from the first surface thereof to the substrate, because the resin coating layer absorbs light. Therefore, in order to securely bond the ink channel walls to the substrate, the light needs to reach a second surface of the resin coating layer that is in contact with the substrate. This allows a portion of the resin coating layer (the epoxy resin) that is located close to the substrate to be sufficiently cured, whereby the ink channel walls are allowed to have ink resistance and can be securely bonded to the substrate. Accordingly, since the light is applied to the first surface of the resin coating layer but must reach the surface in contact with the substrate, the following is important to note. A portion of the light that reaches the substrate is attenuated and therefore has appropriate intensity. However, a portion of the light that travels in a surface region of the resin coating layer is not attenuated yet and has excessively high intensity. The portion of the light having excessively high intensity may prevent the discharge ports from being precisely formed. That is, the following problem can occur: the portion of the light having excessively high intensity may damage a pattern for the discharge ports and/or the ink channel pattern. Occurrence of this problem can lead to a variation in the direction in which droplets are ejected and/or a variation in the size of the droplets. This, in turn, may affect an image that is formed with the ink-jet recording head.